1. Field of the Invention
The present invention relates generally to equipment for mixing molten metals. More specifically, the present invention concerns a self-contained, remotely controlled mixer having forced air-cooled impeller shaft bearings.
2. Discussion of Prior Art
In the molding industry, materials are commonly molded into convenient shapes to facilitate their transport. For example, metals such as aluminum and lead are typically molded into stackable ingots of various standard weights (e.g., 65 and 100 lb. bars). In order for metals to be cast in a mold, they must be melted into a molten liquid. This is typically accomplished by heating the metal in large kettles (e.g., some kettles can hold up to 350 tons of metal and reach temperatures in excess of 1200 degrees Fahrenheit). The metals typically include various elements that may separate as they melt (e.g., in some applications various elements are added together to achieve a desired alloy). It is therefore desirable to mix the molten metal in the kettle to achieve a uniform liquid.
Mixers for mixing molten metals in a kettle are known in the art. Prior art mixers include an impeller coupled to a bearing-supported shaft that is rotated by a motor. These prior art mixers are supported on a bridge above the kettle and require an operator on the bridge to adjust the depth of the impeller in the kettle (e.g., hand-cranked height adjustment). They include gear driven transmissions connecting the motor and the shaft and the transmission and the shaft-supporting bearings are cooled in an oil bath. Unfortunately, these mixers are problematic and have several limitations. For example, the gear drives and the bearings frequently overheat causing premature wear that requires significant maintenance and downtime. In addition, it is undesirable to have an operator on the bridge for height adjustments. Moreover, prior art mixers require a separate storage rack to support the mixer when it is not in use. Furthermore, OSHA regulations now require the top of the kettles to be covered (e.g., with a lid) to reduce the escape of fumes from the kettle and prior art bridge-supported mixers are not well adapted for use with a kettle having a lid.